There is widespread use of automatic labelling devices for applying self-adhesive labels of the pressure-sensitive type on a great variety of articles. The labels may be preprinted or printed just prior to application of labels to articles. The self-adhesive pressure-sensitive type of label is usually provided in supply form by locating the labels in a spaced-apart manner on a backing or carrier web. The web is pretreated to ensure ease of separation from the backing paper. Such treatment may include the use of silicone to permit smooth separation of the label from the backing. To provide the supply of labels for the labelling device, such labels as they adhere to the backing are in the form of a roll which may be placed on a supply reel.
An example of an automatic labelling device using such supply of labels is that manufactured by Accraply Systems, a division of Elcono Corporation of Minneapolis, Minn., and sold under the trademark ACCRAPLY. That device applies self-adhesive labels to articles as they are conveyed past the labeller. In that instance, the label is dispensed by passing the carrier web with labels along a ramp sloped relative to the surface to which a label will be applied and pulling the carrier web around the free end of the ramp or splitter tongue to separate the label from the web. This separation is due to the label being stiffer than the carrier web in combination with the release agents on the carrier web. The separated label is then applied to an article.
A system has been developed to apply labels to file folders, where a plurality of automatic labellers apply labels at predetermined locations on a file. The system is described in co-pending United States patent application Ser. No. 830,118 and Canadian patent application Ser. No. 291,224.
In instances where it is important to ensure precision in applying labels with those devices, the labels must be all of the same length and consistently spaced-apart from each other on the supply roll web. The splicing of the supply of labels also becomes a problem for precision application because the splice must be such to ensure consistent label spacing on web. In making the splice, the label must be precisely positioned over the splice. The adhesive material on the backing web, which holds the splice together, cannot be exposed on the side of web carrying the labels to thereby ensure ease in removal of the label overlying the splice from the backing web on label transfer.
The common approach to sensing the position of the labels on the carrier prior to application is to use a sensing device which senses the position of a label several labels back of the label next to be placed or about to be applied to an article. Based on the assumption that all labels are equally spaced-apart on the backing paper and that there are no missing labels, this creates no problems. In ensuring this equal spacing, the manner of producing the labels becomes very costly, or in the alternative, when equal spacing is not assured, then the precision with which the labels are applied to articles is lost.
It becomes apparent that it would be desirable to determine the position of the label which is about to be applied so that missing labels, inconsistent spacing between labels on the web, or varying lengths of labels would create no problem in the labelling operation. Approaches have been made in the past to sense label position in this manner, such as that disclosed in U. S. Pat. No. 3,801,408. However, in that system the article to be labelled is stationary and the label is applied in a direction transverse to the direction of travel of the article after it is labelled. In that arrangement, the labelling operation functions on the basis that the labeller is actuated to cause the web to move around a device for peeling label from web. During movement of web, the label is sensed and in the same operation the peeled label is picked up by a label transfer pad and applied to the stationary article. With that type of arrangement, it is impossible to obtain precision in applying labels to continuously conveyed articles.
It is, therefore, an object of this invention to provide a labelling system for labelling articles which are conveyed by, past or under the labeller where precision of labelling is achieved regardless, for example, of spacing between and varying lengths of labels on the carrier web. Such system readily accommodates splices in the supply of labels to facilitate operation of the labellers.